Choosing a data type for a value
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. A school database stores a student's postcode, such as 0800 for a remote area. Which data type is best?
2. You want to add up the price of every item in a canteen order, such as $4.50 and $3.95. Which data type suits the price field?
3. You need to sort a list of events from earliest to latest. Which data type should store the event day?
4. A field records whether a student has returned their permission form (yes or no). Which data type is the best choice?
5. Which statement about choosing a data type is correct?
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1postcode: Text | APostcode was given a number type, so the leading zero is dropped and the postcode is now wrong | |
| 2price: Floating point | BStore a postcode as text because you never do maths on it and it can start with 0 (like 0800) | |
| 3Choose the data type by what you will do with the value, such as sorting events in order of when they happen | Chas_paid: Boolean | |
| 4A value that you only test as true or false should use the Boolean type | DStore a price as a number with decimals so you can add, multiply and work out totals | |
| 5postcode: Integer (0800 is stored as 800) | EPrice was given a text type, so values are joined together instead of added, giving a wrong result | |
| 6price: Text (total of $5 + $10 gives "510") | Fevent_date: Date/time |
C
Definitions
data type
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
Postcode: ____
2.
Price (e.g. 12.50): ______________
3.
DateJoined: _________
4.
IsMember: _______
5.
Quantity: _______
Total ← Quantity * 5
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
Table: Customer
B
Postcode : Integer
C
Price : Float
D
Joined : Date/time
Question 2
A
Table: Product
B
Name : Text
C
Price : Float
D
InStock : Text
Question 3
A
Table: Order
B
OrderID : Integer
C
OrderDate : Text
D
Total : Float
Question 4
A
price ← 4.50
B
qty ← "3"
C
total ← price * qty
D
OUTPUT total
Question 5
A
Table: Member
B
Name : Text
C
Postcode : Text
D
Age : Text
Answer Key
Choosing a data type for a value
Section A: Quick Questions
Q1
A — Text, because you never do maths on a postcode
Q2
A — Floating point, because prices have cents
Q3
B — Date/time
Q4
A — Boolean, because the value is only true or false
Q5
B — Choose the type based on what you will do with the value
Section B: Match the Pairs
Q1
postcode: Text → Store a postcode as text because you never do maths on it and it can start with 0 (like 0800)
Q2
price: Floating point → Store a price as a number with decimals so you can add, multiply and work out totals
Q3
Choose the data type by what you will do with the value, such as sorting events in order of when they happen → event_date: Date/time
Q4
A value that you only test as true or false should use the Boolean type → has_paid: Boolean
Q5
postcode: Integer (0800 is stored as 800) → Postcode was given a number type, so the leading zero is dropped and the postcode is now wrong
Q6
price: Text (total of $5 + $10 gives "510") → Price was given a text type, so values are joined together instead of added, giving a wrong result
Section C: Definitions
Q1
data type — Pick the data type by what you will do with the value: calculate (number), sort by date (date/time), test true or false (Boolean). Postcodes are text, not numbers, as you never do maths on them.Section D: Fill in the Blanks
Q1
Postcode: TextQ2
Price (e.g. 12.50): Floating pointQ3
DateJoined: Date/timeQ4
IsMember: BooleanQ5
Quantity: Integer
Total ← Quantity * 5Section E: Spot the Error
Q1
B — Postcodes are never used in calculations, so they should be Text. An Integer drops leading zeros (0800 becomes 800). The line should be Postcode : Text.
Q2
D — InStock is tested as true or false, so it should be Boolean. Text would let any word be stored and makes true/false tests unreliable. It should be InStock : Boolean.
Q3
C — You sort orders by date, so OrderDate needs the Date/time type. As Text, 10/02 would sort before 2/03. It should be OrderDate : Date/time.
Q4
B — The quotes make qty Text, so you can't multiply it by price. A quantity you calculate with should be a whole number: qty ← 3.
Q5
D — Age is used in calculations such as averages and comparisons, so it should be a number. As Text it can't be added or averaged. It should be Age : Integer.